1. Field of the Invention
The invention relates to an opening structure, a manufacturing method thereof, and an interconnection structure; more particularly, the invention relates to an opening structure, a manufacturing method thereof, and an interconnection structure applicable to a three-dimensional (3D) semiconductor device.
2. Description of Related Art
With the integration of semiconductor devices, in order to achieve high density and high performance, development of semiconductor devices in the three-dimensional (3D) space within a limited unit area has become the trend. Common 3D semiconductor devices include 3D-NAND flash memories of the non-volatile memories.
In an exemplary 3D-NAND flash memory, a multi-layer pad structure shaped as a staircase allows contacts to be respectively connected to different film layers in a multi-layer device. Since the aspect ratio of the shallowest contact significantly differs from the aspect ratio of the deepest contact, an etching process for forming the contacts requires an etch stop layer.
If the number of layers of the multi-layer pad structure is relatively small, the etching process for forming the contacts can properly stop on the etch stop layer. Nevertheless, as the number of layers of the multi-layer pad structure shaped as a staircase increases, the thickness of the etch stop layer need be increased significantly, such that the etching process for forming the contacts can properly stop on the etch stop layer.
Thereby, the significant increase in the thickness of the etch stop layer leads to the reduction of the space of the contacts and the resultant reduction of the process window. As such, the contacts cannot be effectively connected to the pads.